I’ve discovered something quite misleading on Amazon.com that has been responsible for 2 failed molding attempts thus far.
When purchasing Oomoo30 from Amazon they suggest Universal Mold release.
It’s a pretty good idea. You don’t want your mold sticking to your part or the retaining walls and mold release is meant to prevent things from adhering to one another.
But while I was making my 2 part mold using Oomoo 30 silicone molding compound I discovered that the 2 halves stuck together pretty badly. I tore the halves a bit while trying to get them apart and the mold was pretty unusable. I chalked it up to inexperience. For my second attempt, I sprayed the heck out of my first mold half and let it sit for 15 minutes to dry before I hit it with a thick second coat. I wasn’t going to fall into the same trap again.
I had to tear that second mold apart in tiny chunks.
You see, it seems that Universal Mold Release is a silicone based product. And you run into a problem when you’re using a layer of silicone to prevent silicone from sticking to silicone. One of the beautiful things about silicone rubber is that it barely sticks to anything other than itself.
So buying Amazon’s recommended mold release actually had me spraying on a layer of primer, creating a better silicone bonding surface.
Don’t use a silicone based mold release when creating a silicone mold.